Retractable safety belts

ABSTRACT

Retractable safety belt apparatus in which a strap is extended from a reel to a selected length and in which the apparatus is thereafter locked automatically to prevent further extension of the strap. Disclosed are: various mechanisms for controlling the operation of the extension-preventing device, including mechanisms driven by the reel and mechanisms responsive to strap tension; different types of strap claimps which open automatically during retraction of the strap and close automatically after desired extension of the strap, including a slider clamp and a clamp with a unidirectionally rotating clamp element; mechanisms which facilitate retraction of the strap; a mechanism which temporarily disables the extension-preventing device to permit the user to lengthen the belt after it has been fastened; and a belt fastener which ensures by a over-movement of fastener elements that the extended strap will always retract a bit after the belt is fastened.

United States Patent Board et al.

RETRACTABLE SAFETY BELTS Inventors: Richard G. Board, 3000 Connecticut Ave., Washington, DC. 20008; Nelson H. Shapiro, 640 Washington Bldg., Washington, DC. 20005 Mar. 18, 1974 Related US. Application Data Division of Ser. No. 409,266, Nov. 5, 1964, Pat. No.

3,817,473, and a continuation-in-part of Ser. No. 377,344, June 23, 1964, Pat. No. 3,289,970.

US. Cl. 242/l07.4; 297/388 Int. Cl. B65h 75/48 Field of Search 242/107 R, 107.2, 107.3,

References Cited UNITED STATES PATENTS Stoffel 292/107.4

Primary Examiner-Edward J. McCarthy Attorney, Agent, or FirmShapiro and Shapiro [57] ABSTRACT Retractable safety belt apparatus in which a strap is extended from a reel to a selected length and in which the apparatus is thereafter locked automatically to prevent further extension of the strap. Disclosed are: various mechanisms for controlling the operation of the extension-preventing device, including mechanisms driven by the reel and mechanisms responsive to strap tension; different types of strap claimps which open automatically during retraction of the strap and close automatically after desired extension of the strap, including a slider clamp and a clamp with a unidirectionally rotating clamp element; mechanisms which facilitate retraction of the strap; a mechanism which temporarily disables the extension-preventing device to permit the user to lengthen the belt after it has been fastened; and a belt fastener which ensures by a over-movement of fastener elements that the extended strap will always retract a bit after the belt is fastened.

14 Claims, 50 Drawing Figures US. Patent Dec. 16,1975 Sheetlof 15 3,926,385

US. Patent Dec. 16,1975 Sheet 2 of 15 3,926,385

US. Patent Dec. 16, 1975 Sheet 3 of 15 3,926,385

US. Patent Dec. 16,1975 Sh66t4 of 15 3,926,385

F l6. l0

U.S. Patent Dec. 16, 1975 Sheet50f15 3,926,385

Sheet 6 of 15 3,926,385

US. Patent Dec. 16, 1975 US. Patent Dec. 16, 1975 Shflfit 7 of 15 3,926,385

TO FASTENER TO REEL US. Patent Dec. 16,1975 Sheet 8 of 15 3,926,385

TO FASTENER TO REEL US. Patent Dec.16,1975 SheetQoflS 3,926,385

US. Patem Dec. 16. 1975 Sheet 10 0f 15 3,926,385

US. Patent Dec. 16,1975 Sheet11of15 3,926,385

US. Patent Dec. 16, 1975 Sheet 12 of 15 3,926,385

US. Patent FIG. 42

Dec. 16, 1975 Sheet 13 0f 15 U.S. Patent Dec. 16,1975 Sheet 14 of 15 3,926,385

26 CENTRIFUGAL 62 CLUTCH US. Patent Dec. 16, 1975 Sheet 15 of 15 3,926,385

RETRACTABLE SAFETY BELTS This is a divisional application of Ser. No. 409,266, filed Nov. 5, 1964, now US Pat. No. 3,817,473, and a continuation-in-part of Ser. No. 377,344, now US. Pat. No. 3,289,970, filed June 23, 1964 for Retractable Safety Belts.

This invention relates to retractable safety belts and more particularly to so-called retractable seat belts for use in automotive vehicles.

The foregoing copending application discloses and claims retractable seat belt apparatus in which a strap having a fastener member at a free end thereof may be grasped by the user and extended from a retraction device to place the strap in user-restraining position, whereupon further extension of the strap is prevented automatically in response, for example, to the cessation of extensile movement or to slight retractile movement of the strap. At the user-restraining position the strap may have any selected length within a wide range of lengths, so as to accommodate varying conditions of user size and clothing. The fastener member is engaged with a mating fastener member in order to complete the belt. When the fastener members are disengaged, the strap retracts automatically. The present application discloses and claims improvements and modifications in such apparatus and discloses and claims related apparatus. A

It is accordingly a principal object of the invention to provide improved retractable seat belt apparatus and the like.

Another object of the invention is to provide improved retractable seat belt apparatus in which a strap may be readily extended to any selected length within a wide range of lengths, locked automatically against further extension, and retracted automatically when released.

A further object of the invention is to provide improved apparatus for clamping and for controlling the clamping of a strap and the like.

Another object of the invention is to provide improved apparatus for holding a clamp open during extension of a strap to a desired length and for automatically permitting the clamp to close thereafter.

Still another object of the invention is to provide improved apparatus for retractable seat belts and the like which is responsive to changes in tension of a strap.

Another object of the invention is to provide improved apparatus for facilitating retractile movement of a strap through a clamp which prevents extensile movement.

Yet another object of the invention is to provide improved apparatus for ensuring some retraction of a strap after extension thereof to a selected length in order to condition a strap clamp to prevent further extension of the strap.

An additional object of the invention is to provide improved retractable seat belt apparatus and the like employing a clamp of the type in which a strap is wound about a clamping pin for exerting a force thereon to clamp the strap in response to an extensile pull.

Still another object of the invention is to provide, in apparatus of the foregoing type, improved means for holding the clamping pin in an open position during ex tension of the strap to a desired length.

A further object of the invention is to provide retractable seat belt apparatus which is normally locked against extension when in user-restraining position but which incorporates means for permitting extension without unfastening the belt, while preventing retraction, so that the user may have ready access to his pockets.

A principal object of the invention is to provide retractable seat belt apparatus and the like having a strap clamp with a clamping pin about which the strap is trained, the clamp being turned automatically to a position at which the clamp is open when the strap is retracted, remaining in thatposition during extension of the strap, and being turned automatically to a position at which the clamp is closed when the extensile movement of the strap ceases.

An additional object of the invention is to provide apparatus of the foregoing type requiring only a spring for moving the clamp to its open position when the strap is retracted.

Still another object of the invention is to provide retractable seat belt apparatus of the foregoing type which utilizes variations in the forces in the strap extending from the clamping pin to provide the desired locking action.

Yet another object of the invention is to provide improved retractable seat belt apparatus and the like employing a feeler mechanism for sensing the amount of strap wound upon a retraction reel and for controlling a strap clamp accordingly.

Still another object of the invention is to provide retractable seat belt apparatus employing a sector driven by a retraction reel for controlling the operation of a strap clamp.

A still further object of the invention is to provide retractable seat belt apparatus in which a relatively small pivotal movement of a strap clamp is sufficient to place the clamp in open or closed position.

An additional object of the invention is to provide retractable seat belt apparatus and the like employing improved pivoting or sliding clamp apparatus.

A still further object of the invention is to provide, in retractable seat belt apparatus and the like, improved means for reducing undesired friction in the movement of a strap past a clamp element.

To summarize briefly, and without intent to limit the scope of the invention, a preferred embodiment of the invention employs in conjunction with a retraction reel, a strapclamp which moves automatically to an open position when the strap is retracted, which remains in that position when the strap is extended to a desired length, and which thereafter moves automatically to a closed position at which extension is prevented, the strap retracting automatically when unfastened.

The foregoing and other objects, advantages, and features of the invention, and the manner in which the same are accomplished will become more readily apparent upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings, which illustrate preferred and exemplary embodiments, and wherein:

FIG. -1 is a perspective view illustrating the external appearance of housing, strap, and fastener components of a typical embodiment of retractable seat belt apparams in accordance with the invention;

FIG. 2 is a plan view illustrating one embodiment of apparatus which may be contained within the housing shown in FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a similar sectional view illustrating a different condition of the apparatus;

FIG. 4A is a similar sectional view illustrating still another condition of the apparatus;

FIG. 5 is a plan view of another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 6 is a sectional view taken along line 6-6 of FIG. 5;

FIG. 7 is a similar sectional view illustrating another condition of the apparatus;

FIG. 8 is a plan view illustrating another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 9 is a sectional view taken along line 9-9 of FIG. 8;

FIG. 10 is a similar sectional view illustrating another condition of the apparatus;

FIG. 11 is a similar sectional view illustrating a modification;

FIG. 12 is a perspective view of a detail of the apparatus of FIGS. 8-11;

FIG. 13 is a plan view of another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 14 is a sectional view taken along line 14-14 of FIG. 13;

FIG. 15 is a similar sectional view illustrating another condition of the apparatus;

FIG. 16 is a similar sectional view illustrating still another condition of the apparatus;

FIG. 17 is a sectional view of another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 18 is a similar sectional view illustrating a different condition of the apparatus;

FIG. 19 is an elevation view, partly in section, illustrating improved fastener apparatus which may be employed in the invention;

FIG. 20 is a plan view, partly in section, of the apparatus of FIG. 19;

FIG. 21 is a sectional view of a detail of strap clamping apparatus in accordance with one concept of the invention;

FIG. 22 is a plan view of the apparatus of FIG. 21;

FIG. 23 is a sectional view of a modified form of clamp apparatus;

FIG. 24 is a sectional view of still another form of clamp apparatus;

FIG. 25 is a sectional view of yet another form of clamp apparatus.

FIG. 26 is a plan view of still another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 27 is a sectional view taken along line 27-27 of FIG. 26;

FIG. 28 is a similar sectional view illustrating another condition of the apparatus;

FIG. 29 is a similar sectional view illustrating still another condition of the apparatus;

FIG. 30 is a plan view of another embodiment of the apparatus which may be contained within the housing of FIG. 1; I

FIG. 31 is a sectional view taken along line 31-31 of FIG. 30;

FIG. 32 is a plan view of another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 33 is a sectional view taken along the line 33-33 of FIG. 32;

FIG. 34 is a similar sectional view illustrating another condition of the apparatus;

FIG. 35 is a sectional view of another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 36 is a similar sectional view illustrating a different condition of the apparatus;

FIG. 37 is a sectional view of a modified form of apparatus which may be contained within the housing of FIG. 1;

FIG. 38 is a plan view of another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 39 is a sectional view taken along line 39-39 of FIG. 38;

FIG. 40 is a similar sectional view illustrating another condition of the apparatus;

FIG. 41 is a similar sectional view illustrating still another condition of the apparatus;

FIG. 42 is a sectional view of another embodiment of apparatus which may be contained within the housing of FIG. 1;

FIG. 43 is a similar sectional view illustrating another condition of the apparatus;

FIG. 44 is a sectional view of another embodiment of the apparatus which may be contained within the housing of FIG. 1;

FIG. 45 is a similar sectional view illustrating a different condition of the apparatus;

FIG. 46 is a plan view of a modification of the apparatus of FIG. 2;

FIG. 47 is a plan view of still another modification of the apparatus of FIG. 2;

FIG. 48 is a sectional view taken along line 48-48 of FIG. 47; and

FIG. 49 is a similar sectional view illustrating another condition of the apparatus.

Referring to the drawings, as shown in FIG. 1 a retractable seat belt of the invention may comprise a strap 10 of suitable material, such as nylon webbing, adapted to be extended from a housing 12 and to be retracted into the housing. The housing may be supported upon the floor of a vehicle, in any convenient orientation, at one side of a seat, or if the seat is strongly anchored to the floor, the housing may be supported directly upon the seat. A free end of strap 10 is provided with a fastener member 14, which in the form shown, is a conventional tongue having locking openings 16. The tongue is adapted to engage a mating fastener member 18, such as a conventional buckle into which the tongue is inserted to complete the belt. As is well known in the art, when the tongue is inserted into the buckle, locking abutments of the buckle enter the openings 16 of the tongue to retain the fastener members in locked engagement until a release element, such as a pivoting lever 20, is operated. Buckle 18 may be connected to another strap, 22, the remote end of which (not shown) may be anchored to the floor (or to the seat) at the opposite side of the seat. Under appropriate circumstances strap 22 may be dispensed with and the mating fastener member 18 may be supported directly upon the seat or otherwise anchored to the floor.

In accordance with the invention it is desired that the strap be readily extensible from the housing 12 to place the strap in user-restraining position, then be locked against further extension automatically, and flnally be retracted into the housing when released. Moreover, it is desired that strap l0 be capable of extension to any desired length within a wide range of lengths, so that all adjustments in length to accommodate different size users and different clothing conditions may be made by the strap 10. Strap 22 may then be kept very short or may be eliminated as indicated above.

FIGS. 2, 3, 4 and 4A illustrate one embodiment of an apparatus which may be employed in the housing 12 in order to accomplish the foregoing purposes. As shown in FIG. 2, a frame comprising a pair of side plates 24 and 26 supports a retraction reel 28. The frame may be secured to or form part of the housing and should be anchored to the floor or, under appropriate circum stances, to the seat. The reel comprises a pair of end discs 30 and 32 joined by a sleeve hub 34, the end discs being provided with suitable bearings, as is well known in the art, for rotatably supporting the reel upon a pin 36 which extends through the sleeve hub with substan tial space therebetween. A spring motor for winding the reel may comprise a helical torsion spring 38 which is slipped over the pin 36 with substantial free play. One end of the spring may be secured to an end disc or the sleeve hub and the other end to the pin 36, so that the spring is wound as the reel is turned relative to the pin. Other well known types of retracting reels may also be employed.

Strap 10 has the end remote from fastener member 14 attached to the hub of the reel so that the strap may be wound upon the reel by the reel spring for retraction and may be extended from the reel while winding the 4 spring. In the form shown the strap is trained from the bottom of the reel.

In order to prevent extension of the strap a clamp 40 is employed. In the form shown the clamp comprises a convexly contoured clamping plate 42 supported by a cross bar 44 between the side plates 24 and 26. Plate 42 has a pair of side members 46 which along with plate 42 constitute a yoke for supporting a pivoting clamp member 48. Clamp member 48 is supported upon a pin 50 extending between the side members. A torsion spring 52 received within a bore at one end of the pivoting clamp member, and having its respective ends connected to one of the side members 46 and to the clamp member, biases the clamp member toward a position at which a clamping surface 54 engages the strap 10 as shown in FIG. 4A. The clamping surface may be roughened, knurled, or longitudinally grooved so as to facilitate the clamping action, as well known in the art. Clamping surface 54 is shaped so as to increase the clamping pressure in response to extensile strap pull. This is accomplished by suitably shaping the clamping surface, as by making the trailing edge of the clamping surface a greater distance from the pivot 50 than the leading edge. The clamp per se is well known in the seat belt art, being utilized in the buckle of airplane type or metal-to-webbing type belts.

From the foregoing description it is apparent that if clamp 40 is held open, the strap may be extended freely, and if clamp 40 is held closed, extension will be prevented. Because of the design of the clamp, as indicated above, retractile movement of the strap tends to drag the clamp open against the bias of spring 52 so as to permit the strap to be retracted even when the clamp has moved to the closed position shown in FIG. 4A. This action is facilitated by contouring the teeth or corrugations of the clamping surface so that they are in clined rearwardly for ready engagement with the strap when the strap is extended but to minimize engagement when the strap is retracted.

In order to open the clamp so that the strap may be extended to the desired length a feeler 56 is employed for sensing the amount of strap wound upon the reel. In the form shown the feeler comprises a lever arm extending from the pivoting clamp element 48, being secured to the top thereof by a small block 58. It will be seen that when the reel is sufficiently filled the strap thereon engages the free end of the feeler and lifts the feeler so as to turn the clamp member 48 to open it as shown in FIG. 3. When the strap is sufficiently extended from the reel, the feeler is free of the strap as shown in FIG. 4A, and the clamp is permitted to close. The feeler may be shaped so as to engage the strap wound upon the reel within a predetermined range of wound strap. For example, the feeler may engage the strap until the strap has been withdrawn from the reel about eighteen inches and then be free of the strap.

The feeler opens the clamp to permit initial extension of the strap but will not maintain the clamp open after initial extension. In order to maintain the clamp open until the strap has been extended approximately to its user-restraining length an additional mechanism is employed. In the form shown this mechanism comprises one or more sectors 60, 62 driven by the reel. The sectors are pivotally supported by stub shafts 64 upon the side plates of the frame and engage the periphery of the end discs of the reel, which may be provided with rubber O-rings 66 preferably seated in grooves on the peripheral surface of the end 'discs. The sectors are connected by a pin 68, so that they move in unison and are provided with a tension bias spring 70, one end of which may be connected by a screw to the top of one sector and the other end of which may be connected by a screw to the block 58.

When the strap is extended, the reel turns counterclockwise as shown in FIG. 4, lifting the sectors and engaging pin 68 with the undersurface of. the feeler in order to hold the clamp open even after the feeler loses contact with the webbing. At this position the lower edge of the sector surface is just maintained in contact with the reel, presenting a slight drag on the reel. The strap is extended to approximately the desired length, and the tongue 14 (FIG. 1) is engaged with the buckle 18. In so doing it is almost impossible to avoid extending the strap slightly more than the length required when the tongue and buckle are later snugly against the users body. Thus, after the tongue is engaged with the buckle, strap 10 is always retracted slightly, the reel turning in a retractile direction, clockwise in FIG. 4A. When this occurs, the sectors turn away from the feeler, permitting the clamp to close. Any further extensile movement of the strap is now prevented. As shown in FIG. 4A the sectors may actually lose contact with the reel by a slight amount and come to rest upon the supporting bar 44, the tension in bias spring 70 being negligible at this time. Thus, in a collision, even if the strap were to slip slightly through the clamp before the clamp engaged firmly there would be no possibility of the sectors being driven by the reel to open the clamp.

If now the tongue is disengaged from the buckle. the reel retracts the strap, dragging it through the clamp. which opens slightly due to the retractile movement, and eventually the feeler 56 engages the strap as shown in FIG. 3, turning the clamp element 48 clockwise in that figure to open the clamp more fully. This turning movement of the clamp element increases the tension in bias spring 70 enough to engage the upper edge of the sectors with the reel, but the drag on the reel is minimal. When the strap is extended again, the sectors are immediately raised to the position of FIG. 4.

The amount of retractile movement of strap 10 required to permit the clamp to close is very slight, of the order of A inch, and depends upon how much webbing remains on the reel and the relative radii of the reel and the sectors. The mechanical advantage of the feeler and the sectors determines the back pressure upon the reel, which has been found to be quite low. By utilizing a roller at the end of the feeler engaging the strap, as will be later described, the drag upon the reel created by the feeler is further reduced.

FIGS. 4749 illustrate a modification in which the clamp is additionally opened when a strap is retracted a predetermined amount so as to facilitate flow of the strap through the clamp during further retraction. As shown, this may be accomplished by providing additional sectors 69 driven by the reel. These sectors are supported on stub shafts 71 from the side plates of the frame and have a bail 72 pivotally suspended therefrom at the side of the stub shafts remote from the reel. While the strap is being extended, the sectors 69 are in the full line position of FIG. 49, and there is substantial space between the bail 72 and the feeler. The slight retractile movement of the strap required to permit the clamp to close is not sufficient to engage the bail with the feeler, the sectors 69 moving to the phantom line position. However, further retractile movement causes the bail to lift the feeler very slightly but enough to facilitate the retractile movement of the strap through the clamp. If the strap is permitted to retract sufficiently to engage the bail 72 with the feeler and then is pulled again in an extensile direction, the slight extensile turning movement of the reel will disengage bail 72 from the feeler and permit the clamp to close instantly. The lifting movement of the feeler by the bail 72 is preferably made insufficient to create enough tension in bias spring 70 to engage sectors 60 and 62 with the reel. The relative degrees of rotation of the pairs of sectors may be controlled by varying their radii and/or by engaging the pairs of sectors with different diameter portions of the reel; the end discs may be stepped down accordingly to provide shoulders for engaging the respective pairs of sectors.

FIGS. 19 and 20 illustrate the manner in which strap fastener members may be modified to ensure sufficient retraction of the strap to operate the clamp of a retraction-responsive apparatus. As shown, either or both parts of the fastener couple may be constructed so as to provide lost motion. Thus the tongue fastener member 14A may have a shell 73 into which the tongue proper 74 may telescope. The shell is attached to the strap 10 and the tongue is normally urged out of the shell, as by compression springs 76. Thus if the tongue is inserted in a conventional buckle, the resistance to insertion created by the latch members of the buckle will cause the shell 73 to telescope about the tongue 74 before the tongue is forced into the buckle. After the tongue has been engaged with the buckle, the shell will be free to 8 move in the reverse direction under the bias of springs 76 to create some slack in the strap 10, which will be taken up by the retraction reel.

The same type of telescoping action may take place in the buckle 18A. When a tongue is inserted into the opening 78, the latch abutment 80 will retreat along the buckle shell along with the release lever 82, the pivots 84 of which slide in slots 86 in the sides of the buckle shell as a spring 88 is compressed. Finally the insertion pressure exerted by the tongue will be sufficient to turn the abutment 80 upward against its usual bias spring, not shown, to permit the tongue to slip under the abutment so that the abutment may enter the opening in the tongue. Then the tongue is moved reversely by spring 88 so as to create slack in strap 10 which is taken up by the retraction reel. Other types of lost motion fastener members may also be employed to create slack to be retracted.

FIG. 46 illustrates a modification of the apparatus of FIG. 2 in which the end discs of the reel are split into two parts 30A, 30B, and 32A, 323. The B parts are fixed to the hub of the reel and turn integrally therewith, while the A parts are coupled to the B parts by centrifugal clutches contained within the end discs. The clutches may be of any conventional type well known in the art for coupling a pair of rotary members when one of them is turned and for decoupling the members when that one stops. Under these circumstances the sectors 60 and 62 will not move up to engage the feeler 56 until the reel proper has turned somewhat, the feeler 56 holding the clamp open until the sectors take over this function, When the reel ceases its extensile movement, the disc portions 30A and 32A will be decoupled therefrom, so that the pressure of the feeler upon the sectors, due to the bias spring 52 of the clamp, will permit the sectors to move down, turning the disc portions 30A and 32A relative to the reel and closing the clamp without requiring retractile movement of the strap.

FIGS. 5, 6, and 7 illustrate another embodiment of the apparatus which may be placed in housing 12 of FIG. 1. A retraction reel 90, which may be of the type previously described, is rotatably supported upon a frame 92. The strap 10 extends from the bottom of the reel past a clamp 94 comprising a fixed clamp plate or block 96 and a pivoting clamp element 98. Element 98 is pivotally supported at one side of a shaft 100 extending between the side plates of the frame and has a lever arm 102 at the opposite side of shaft 100 supporting a strap guide roller 104 arranged to indent the strap. Guide rollers 106, and 108 are rotatably supported upon the frame at opposite sides of roller 104, so that the strap passes reversely about roller 104. An additional guide roller 110 may be provided to guide the strap across the fixed clamp element 96.

When the strap is extended, the resulting tension in the strap exerts a pressure on roller 104 and turns lever arm 102 so as to bring the clamping surface 112 of clamp element 98 into engagement with the strap, overcoming a return spring 114, which maintains the clamping surface 112 away from the strap when there is reduced tension in the strap.

A feeler 116 is pivotally supported by a pin 118 upon the frame and has an arm 120 arranged to interfere with the movement of clamp member 98 when sufficient strap is wound upon the reel. As shown. the free end of arm 120 may enter a small notch 122 formed in the surface of clamp member 98. A return spring 124 

1. A retractable seat belt comprising a retraction reel, a strap connected to said reel for retraction and extension, clamp means for preventing extension of said strap, said clamp means comprising a pair of clamp elements, one of said elements being movable relative to the other, said one element comprising a slider, said strap being trained from said reel between said clamp elements and around said slider reversely whereby tension in said strap exerts a force upon said slider tending to move said one clamp element toward the other, means responsive to the amount of strap wound upon said reel for moving said one clamp element away from the other, and means for maintaining said one clamp element away from the other until said strap is extended to a desired length.
 2. The retractable seat belt of claim 1, further comprising guide means for guiding said strap between said clamp elements in a direction transverse to the movement of said slider, said slider having a roller around which said strap is trained.
 3. The retractable seat belt of claim 1, the last-mentioned means comprising a lever arranged for pivotal movement about a fulcrum, said lever being coupled to said slider adjacent to said fulcrum, and means responsive to movement of said reel for engaging said lever remote from said fulcrum and turning it to move said slider.
 4. The retractable seat belt of claim 1, the last-mentioned means comprising a sector driven by said reel.
 5. The retractable seat belt of claim 1, further comprising bias means for urging said one clamp element away from said other clamp element.
 6. In a retractable seat belt, retraction means, a strAp connected to said retraction means for retraction and extension, clamp means for preventing extension of said strap, means for rendering said clamp means ineffective until said strap is extended to a selected length and for thereafter rendering said clamp means effective to prevent extension of said strap, said retraction means tending to retract said strap when said strap has been extended to said selected length, and means for temporarily rendering said clamp means and said retraction means ineffective after said strap has been extended to said desired length, whereby said strap may be further extended without retraction, and for thereafter rendering said clamp means and said retraction means effective again whereby said strap will be automatically retracted to said selected length.
 7. The seat belt of claim 6, the last-mentioned means comprising pawl and ratchet means temporarily engageable to prevent retractile movement of said retraction means and means for opening said clamp means concurrently with the engagement of said pawl and ratchet means.
 8. A retractable seat belt comprising retraction means, a strap connected to said retraction means for retraction and extension, said strap having a fastener member at a free end thereof, a mating fastener member adapted to engage the first-mentioned fastener member to place said belt in user-restraining position means for preventing extension of said strap, means for rendering said extension-preventing means ineffective while said strap is being extended to a desired length, means responsive to retractile movement of said strap thereafter for rendering said preventing means effective, and means associated with said fastener members for causing at least a portion of the first-mentioned fastener member to move in an extending direction beyond said user restraining position in order to engage the mating fastener member and thereafter to move in a retracting direction to provide said retractile movement.
 9. In a retractable seat belt and the like having a strap adapted to be extended and retracted, clamping means for preventing extension of said strap, said clamping means comprising a pair of clamp elements, one of said elements being movable toward and away from the other of said elements, said strap being trained between said elements and around said one element, said one element being supported for rotation in at least one direction when said one element is away from the other element, and means for preventing rotation of said one element in a direction corresponding to extensile movement of said strap when said elements are brought together to clamp said strap.
 10. The apparatus of claim 9, said one element comprising a roller and said preventing means comprising a ratchet wheel attached to said roller and a pawl adapted to engage said ratchet wheel.
 11. The apparatus of claim 10, said pawl being supported for movement with said one element toward and away from said other element and permitting rotation of said roller in said one direction only.
 12. The apparatus of claim 11, said ratchet wheel being supported for movement toward and away from said pawl as said roller moves toward and away from said other element and being located for engagement with said pawl when said roller is adjacent to said other element and for preventing extensile rotation of said ratchet wheel.
 13. The apparatus of claim 9, said one element being supported for pivotal movement toward and away from said other element.
 14. The apparatus of claim 9, said one element being supported for reciprocative movement toward and away from said other element. 